1. Field of the Invention
The present invention relates to an injector assembly designed for expelling a material held in a barrel, as well as a plunger and a seal member used for the injector assembly.
2. Discussion of the Background
As used throughout the description, the injector assembly is a broader term which includes a syringe assembly.
The injector assembly includes a tubular barrel having a proximal end forming an opening through which a material is introduced into the barrel, and a distal end forming a material discharge port (hereinafter sometimes simply referred to a barrel discharge port) through which the material accommodated in the barrel is expelled to the outside; a plunger having a distal end positioned within the barrel and a proximal end projecting outwardly from the opening at the proximal end of the barrel; and a seal member connected with the distal end of the plunger so as to be held in sealing engagement with the inner circumference of a center hole of the barrel and axially slidable therealong according to axial movement of the plunger. The seal member is slid towards the distal end of the barrel through the plunger so that the material such as a drug solution filled in the barrel is expelled through the discharge port.
In the meantime, the injector assembly of the above conventional type poses the following problems when used with a liquid or pasted material used in dentistry field, such as dentifrice, tooth surface treatment material, bonding material, sealant material and repairing material. That is, when sliding the seal member towards the distal end of the barrel by applying pressing force onto the plunger, a part of the material held between the seal member and the barrel discharge port is expelled to the outside, while the residual part of the material remains and is compressed between the seal member and the barrel discharge port. Hence, the residual part of the material has retained elasticity (residual pressure).
Accordingly, at the time just after finishing the discharging of the material by releasing pressing force from the plunger, there may occur a problem that a part of the material is leaked through the barrel discharge port due to the retained elasticity of the compressed material (subsequent dripping).
Also, as another problem, when the injector assembly is used with the above described dental preparations, air bubbles may mix into the material during it is filled in the barrel due to high viscosity of the dental preparations.
In the conventional injector assembly, a grip used in pressing the plunger is formed integrally with the barrel without fully considering operability.
The present invention has been conceived in light of the above problems. It is an object of the present invention to provide an injector assembly that has a simple structure capable of effectively preventing subsequent dripping, as well as a plunger and a seal member used for the injector assembly.
It is another object of the present invention to provide an injector assembly that has a simple structure capable of effectively preventing subsequent dripping, while effectively discharging air bubbles mixed in a material held therein, as well as a plunger and a seal member used for the injector assembly.
It is still another object of the present invention to provide an injector assembly that is capable of improving operability while producing the above effects.
In accordance with the present invention, there is provided a plunger for being inserted in a tubular barrel in an axially movable manner, which includes a plunger body having a distal end positioned within the barrel and a proximal end positioned outside of the barrel, and a seal member disposed on the distal end of the plunger body. The seal member has a base portion extending from the plunger body towards the distal end of the barrel, and a flange portion radially outwardly extending from the base portion and having a peripheral edge contacting an inner circumference of the barrel so as to define an accommodation space within the barrel. The flange portion is elastically deformed to be brought into an elastically deformed state by means of reaction force from a material accommodated within the accommodation space when the seal member is slid towards the distal end of the barrel by means of pressing force applied onto the plunger body so as to force the material out of the accommodation space, and presses the plunger body back towards the proximal end of the barrel by means of self-restoring force of the flange portion when the pressing force is released from the plunger body.
With the plunger having the above arrangement, the accommodation space can be automatically expanded subsequent to finishing the material discharging operation. Therefore, residual pressure caused in the material during the discharging operation can be automatically released therefrom. As a result, subsequent dripping of the material from the accommodation space can be effectively prevented.
The plunger body is preferably formed integrally with or separately from the seal member.
The flange portion preferably has a thinner wall part adjacent to the base portion, and a thicker wall part lying on the radially outward side of the thinner wall part so as to contact the inner circumference of the barrel.
Preferably, the flange portion extends radially outwardly from the base portion towards the distal end of the barrel when in an initial state, thereby forming a concave surface facing the distal end of the barrel, and extends radially outwardly from the base portion towards the proximal end of the barrel when in the elastically deformed state, thereby forming a concave surface facing the proximal end of the barrel.
The plunger body preferably includes a stopper member for defining an elastically deformable range of the flange portion.
According to another aspect of the present invention, there is provided a seal member for being interconnected with a distal end of a plunger, which is inserted in a tubular barrel in an axially movable manner. The seal member has a base portion extending from the plunger towards the distal end of the barrel, and a flange portion radially outwardly extending from the base portion and having a peripheral edge contacting an inner circumference of the barrel so as to seal a material accommodated within the barrel. The flange portion is elastically deformed by means of reaction force from the material accommodated within the barrel when the plunger is slid towards the distal end of the barrel by means of pressing force applied on the plunger so as to force the material out of the barrel, and presses the plunger back towards the proximal end of the barrel by means of self-restoring force of the flange portion when the pressing force is released from the plunger.
According to still another aspect of the present invention, there is provided an injector assembly capable of preventing subsequent dripping that includes a tubular barrel having a distal end, to which an applicator can be attached; a plunger being inserted in the barrel in an axially movable manner in such a manner as to have a distal end positioned within the barrel and a proximal end extending outwardly through an opening defined at the proximal end of the barrel; and a seal member disposed on a distal end of the plunger. The seal member has a base portion extending from the plunger towards the distal end of the barrel, and a flange portion radially outwardly extending from the base portion and has a peripheral edge contacting an inner circumference of the barrel so as to define an accommodation space within the barrel. The flange portion is elastically deformed by means of reaction force from a material accommodated within the accommodation space when the seal member is slid towards the distal end of the barrel by means of pressing force applied onto the plunger so as to force the material out of the accommodation space, and presses the plunger back towards the proximal end of the barrel by means of self-restoring force of the flange portion when the pressing force is released from the plunger.
The barrel preferably includes a tubular barrel body, and a grip, which is detachably attached to the barrel in such a manner as not to be axially slidable but to be axially rotatable.
With the barrel having above arrangement, the relative positional relationship of the grip to the barrel body in the circumferential direction can be properly adjusted in each case.
As a result, when a bent needle is employed as an applicator, operability can be improved.
As another preferred embodiment, the color of the grip is varied. In this case, the color of the gripper can serve as an identification means, enabling the material accommodated within the barrel to be correctly identified. As a result, misadministration of the material can be effectively prevented.
Preferably, the barrel body includes a shaft portion and a flange portion radially outwardly extending from a proximal end of the shaft portion. In this arrangement, the shaft portion is provided on an outer circumference thereof with an engagement protrusion, and the grip is engaged with the shaft portion so as to be rotatable around the axis of the shaft portion while being held by the flange portion and the engagement protrusion of the barrel body so as not to slide along the axis of the shaft portion.
According to yet another aspect of the present invention, there is provided a plunger for being inserted in a tubular barrel in an axially movable manner that includes a plunger body having a distal end positioned within the barrel and a proximal end positioned outside of the barrel, and a seal member disposed on the distal end of the plunger body. The seal member has a base portion extending from the plunger body towards the distal end of the barrel, and a flange portion radially outwardly extending from the base portion and having a peripheral edge contacting an inner circumference of the barrel so as to define an accommodation space within the barrel. The flange portion takes an elastically deformed state with the peripheral edge slid along the inner circumference of the barrel towards the proximal end when a material accommodated within the accommodation space has retained elasticity by means of pressing force applied onto the material, and presses the plunger body back towards the proximal end of the barrel and returns to an initial state by means of self-restoring force of the flange portion with the relative positional relationship between the peripheral edge of the flange portion and the inner circumference of the barrel remained fixed when the pressing force is released from the material within the accommodation space. The flange portion forms at lease one recessed area on the peripheral edge, the at least one recessed area faces the distal end of the barrel when the flange portion takes the initial state. The accommodation space is brought into communication with the outside via the recessed area when the flange portion takes the elastically deformed state.
According to another aspect of the present invention, there is provided a plunger for being inserted in a tubular barrel in an axially movable manner that includes a plunger body having a distal end positioned within the barrel and a proximal end positioned outside of the barrel, and a seal member disposed on the distal end of the plunger body. The seal member has a base portion extending from the plunger body towards the distal end of the barrel, and a flange portion radially outwardly extending from the base portion and having a peripheral edge contacting an inner circumference of the barrel so as to define an accommodation space within the barrel. The flange portion takes an elastically deformed state with the peripheral edge slid along the inner circumference of the barrel towards the proximal end when a material accommodated within the accommodation space has retained elasticity by means of pressing force applied onto the material, and presses the plunger body back towards the proximal end of the barrel and returns to an initial state by means of self-restoring force of the flange portion with the relative positional relationship between the peripheral edge of the flange portion and the inner circumference of the barrel remained fixed when the pressing force is released from the material accommodated within the accommodation space. The flange portion forms at lease one recessed area on the peripheral edge. The at least one recessed area tilts closer to a center line of the flange portion, as advancing from the radially inner side towards the radially outer side, so as to face the distal end of the barrel when the flange portion takes the initial state.
An injector assembly capable of preventing subsequent dripping preferably includes a tubular barrel, and the plunger having the above arrangement for being inserted in the hollowed barrel in an axially movable manner.
The barrel preferably includes a tubular barrel body and a grip detachably attached to the barrel body in such a manner as not to be axially slidable but to be axially rotatable.
The barrel body preferably includes a shaft portion and a flange portion radially outwardly extending from a proximal end of the shaft portion. In this arrangement, the shaft portion is provided on an outer circumference thereof with an engagement protrusion; and the grip is engaged with the shaft portion so as to be rotatable around the axis of the shaft portion while being held by the flange portion and the engagement protrusion of the barrel body so as not to slide along the axis of the shaft portion.